DE1953447A1 - Composite bearing shell and process for their manufacture - Google Patents

Description

PATENT LAWYERS OR. MOLLER-BORg DIPL.-ING. GRALFS

DR. MANtTZ · DR. DEUFEL 1 MÖNCHEN 22, HOBERT-KOCH-Sm 1 “. . _n . _ar

phone 226110 ² ^ · October

Lo-Sv - G 2027

GENERAL MOTOHS CORPORATION Detroit, Michigan, USA

Composite bearing shell and process for their manufacture

Priority: USA, October 29, 1968, No. 771,4-16

The invention relates to the processing of aluminum-based bearing material, which is used for bush bearings and the like. suitable is. In particular, the invention relates to aluminum bearing alloys which have a distributed phase soft metal, and a method for processing such alloys, the soft phase being im general flat-elongated platelets is formed, which are substantially parallel to the Lagerober'lache are. The orientation of the platelets in the finished bearing part is carried out and controlled in such a way as to be most advantageous Location of the soft phase with regard to the storage effect.

In the USA patent 3 4-10 331 and the corresponding German patent application P 15 58 249.7, a method for producing a cast bearing alloy is described which generally contains spherical particles of lead which are distributed in an aluminum matrix.

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Here, a strip of lead-containing aluminum-based alloy is cast in a manner by which dl · concentration of lead increases in a direction from one surface of the strip to the opposite surface. The distribution of the tiny lead particles in an aluminum matrix makes an excellent bearing material, in particular for use in bushing bearings and the like. In general, the cast aluminum strip eventually becomes connected to a steel support strip for carrying, whereby the side of the aluminum strip with a low lead concentration is connected to the steel base and the The side of the aluminum strip with a high concentration of lead becomes the bearing surface. Storage materials of the described Composition and structure have excellent storage properties as a result of the dispersion of the soft ice in the Aluminum matrix. In fact, it has been found that bush bearings of this type have properties that match those the more expensive bush bearings: made of lead-free aluminum alloy with a coating of bearing material are provided, are equivalent or superior.

The invention aims to provide an improved method of processing an aluminum-based cast aluminum alloy which makes it possible to overcome the problem of increased resistance against scoring for the bearing surface, and to overcome the embedding of foreign particles in them.

According to a preferred embodiment of the invention, can This problem can be solved »by first casting a strip of an aluminum-based alloy, which is disclosed herein a dispersed phase ▼ <> & finely divided, in general containing spherically shaped particles made of a soft metal, e.g. lead, In general it is preferred that the cast strip is made as described in U.S. Patent 3,410,331 so that the

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Concentration of soft metal (lead) in one direction from one of the major surfaces of the cast strip to the other rises. The cast strip is machined to suitable predetermined dimensions machined or otherwise trimmed, and then rolled to obtain a reduction in thickness, and if so It is desired to connect the cast aluminum alloy strip to a suitable support material such as steel.

According to the invention, the cast strip, in order to reduce its thickness, is rolled so that the spherical Particles of soft metal are flattened and these in Direction of rolling can be extended. The thin dimension of Jedcc is a flattened particle or plate roughly perpendicular to the rolled surface, and the broad dimensions of a larger part of the plate lie in or parallel to the plane of the working surface of the stock material.

According to another important embodiment of the invention, after the cast strip has been rolled to elongate the spherical particles, it is cut or sheared into bearing blanks, the cuts being perpendicular to the general direction of the soft metal flakes. This means that when the bearing blank is processed into a finished bearing shell, the platelets made of soft metal extend transversely to the intended direction of rotation of a fitted undulating part in the bearing. In other words, the intended direction of rotation of a wave-shaped part with regard to the finished bearing material lies transversely to the direction in which the bearing material was originally rolled. In this way

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gen the flat, elongated, soft particles across the Movement of the wave-shaped part around the maximum exposed area and the possibility of embedding foreign particles to deliver, which get in between the rotating undulating part and the bearing surface, and to minimize scoring on the bearing surface.

The invention will hereinafter be referred to in particular described on the drawing; in the drawing are:

FIG. 1 is a perspective view of a bimetallic strip connected to one another by rolling Alloy made of aluminum-soft metal, which has a steel base;

FIG. 2 is a perspective view of a bimetallic bushing bearing which has been produced from a blank cut off from the strip of FIG. 1 in the manner shown;

i * igur 3 © ine photomicrograph at 100 times magnification a Part of the surface of the aluminum alloy of the strip connected to one another by rolling ils. 1;

Figure 4 is a photomicrograph at 100X magnification a section of the metal strip of FIG. 1,

viewed from the side; and Figure 5 is a photomicrograph at 100X a section of the bimetallic strip of Figure 1 when viewed from one end.

In the following detailed description of a preferred embodiment of the invention, an aluminum lead alloy according to US Pat. No. 3,410,331, which may optionally be placed on a steel base is rolled on. However, it should be noted that

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sen that the invention is equally applicable to aluminum alloys "watch out for other soft metals as lead, for example cadmium or bismuth, and those that do not necessarily contain a Underlayer are equipped.

The molten alloy was made in an induction furnace, the alloy contained in parts by weight about 4.75% lead, 0.5 % tin, 4 % silicon, 1 % cadmium, 0.10 % magnesium, 0.20% manganese, 0, 10% copper and the rest was aluminum. After being heated to a temperature of about 955 ° C (175O ⁰ F), was the molten metal from the induction furnace into a horizontally mounted, provided with an open end form, · as that in the USA Patent 3,410,331 is reproduced, allowed to flow. The rate of cooling of the metal in the mold was controlled so that the droplets of liquid lead formed in the molten aluminum could migrate under the influence of gravity before the aluminum completely solidified. In this way a dispersion of fine, generally spherical particles of lead was observed across the aluminum matrix, but with a gradient in lead concentration from the top to the bottom of the horizontally cast strip. Since lead has a higher density than aluminum, the concentration of the finely divided lead phase increased in the direction from the top to the bottom of the cast strip. Microscopic examination of the cast strip clearly indicated that the dispersed lead particles were generally spherical in configuration in the strip so cast.

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In this example, the tipped mold was arranged and constructed so that the cast strip was rectangular in cross-section , approximately 9.5 mn (3 / B inch) thick and 133 Λ »η (5.25 inches) wide. A small amount of the material was abraded from both the top and bottom surfaces to produce a strip that had more precisely parallel faces. 200 ft (61 m) sections of the cast strip were rolled into rolls and the bulbs normalized and relaxed. The wound and normalized strip, now slightly less than 9-5 mm (3/8 inch) thick, was passed repeatedly between suitable rollers, reducing the thickness of the strip to about 1.27 mm (0.050 inch). The strip was not allowed to expand significantly in width. Therefore, approximately six times the elongation was obtained. Following the final pass between the rolls, the ends of the strip were trimmed so that its width was equal to the intended length of half the circumference of the final bush bearing to be produced.

After the rolling and trimming operations, the aluminum-soft metal alloy strip was normalized. The rolled and normalized strip was then suitable for rolling together with a hedge layer of low carbon steel. This was done by heating a thin backing strip of steel of practically the same width as the strip made of aluminum to about 650 ^° C (1200 ^° P), placing the aluminum strip and steel strip on top of one another, with the side of the aluminum strip having a low BJ content was placed against the steel strip and then the two strips passed between suitable rollers.

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While the rolling was being carried out, the aluminum strip underwent a further reduction in thickness, approximately 3: 1, and it was connected to the steel base firmly and to the same extent. At this stage, the thickness of the aluminum sheet _H c in the bimetal strip was about 0.41 to 0.46 mm (0.016 "to 0.018"). 1 reproduced. The relative thicknesses of the aluminum material 12 and the steel base 14 are not necessarily shown in detail. As stated above, the strip was rolled lengthways each time so that the finely divided lead particles 16 (which contain some tin and cadmium), which are somewhat exaggerated in size for the purpose of illustration, are flattened in the direction of rolling and be extended. The photomicrograph of Figure 3 shows the broken and flattened lead particles 16 in the aluminum macrix. FIG. 4 is a photomicrograph of a section of the rolled bimetal strip as viewed from the side with the aluminum layer 12 bonded to the steel layer 14. In this case, the lead particles 16 are extremely thin and hardly visible in marked contrast to the generally spherically shaped particles in the alloy cast in accordance with US Pat. No. 3,410,331. It can be seen that the thin lead flakes 16 are practically parallel to the upper surface 18 of the aluminum layer.

Figure 5 is a photomicrograph of a section shown in a plane perpendicular to the rolling direction, or in other words a view from the end of the rolling with each other connected strip. It can be seen that the lead flakes 16 are very thin and generally parallel

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to the exposed surface of the section of aluminum. ;

There are now bearing blanks cut off from the bimetal strip or sheared off. In this example, a smooth bush bearing, as indicated in Figure 2 with 20, and the direction of movement of the matching undulating part is made as by the Arrow shown. Correspondingly, the bearing blanks in this pail are sheared transversely from the bimetal strip. The planks are formed into a semicircular shape, with the aluminum layer 12 on the inside from the support roof 14- Steel lies. At this point, all final machining operations are performed on the warehouse, which may be necessary to bring the object to its final dimensions.

The distributed, soft lead plates 16 in the surface the aluminum layer and which are distributed in this are in Figure 2 with their longest dimension perpendicular or transverse arranged with respect to the rotational movement of a wave-shaped part, and the elongated platelets or fragments of platelets are oriented so that their two major dimensions lie in planes generally parallel to the bearing surface. With this arrangement the phase delivers of the soft lead metal has a maximum embedding capacity for premd particles which are between the moving shaft and the bearing surface are typically drawn in. This takes place because all foreign particles introduced in this way move in a direction transverse to the elongated platelets, and much more likely to enter a soft phase bump. In addition, in the example shown, the soft lead phase is most effective in increasing the strength against scoring of the bearing surface. The

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tendered procedures for the machining of alloys Aluminum soft metal and in particular of alloys made of aluminum-lead provides a bearing material that supports the most of the desirable properties of conventional aluminum-silicon-cadmium bearing alloys with a Soft lead coating for resistance to scuffing and offer for embedding, "however, the composition according to the invention is less expensive to manufacture.

The invention is particularly applicable to cast aluminum-soft metal alloys in which the soft metal is in a separate phase in an aluminum matrix. In general it is necessary and will be preferred that the calibration metal phase in a dispersion of more or less spherical particles in the cast Condition is present. For this to be achieved there must be a suitable temperature range above the temperature at which aluminum solidifies!;, exist in which the molten soft metal has a low solubility in molten aluminum. Therefore the soft metal, when the higher-melting aluminum solidifies, it is drawn into the aluminum matrix in a separate phase. In a preferred embodiment of the invention, the molten soft metal can be brought into the to migrate molten aluminum. around a concentration gradient of the soft metal in the finished casting.

Lead, cadmium and vismut are examples of soft metals which have limited solubility in molten aluminum at temperatures just above the solidification temperature of the aluminum, lead has a maximum solubility of about 1 to 2% by weight in aluminum under these conditions. Bismuth has a maximum solubility of about 3 wt.% In the molten aluminum, cadmium and forms a separate

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liquid phase in molten aluminum (at temperatures just above the melting point of aluminum) when it is in amounts greater than about 8 to 9 wt. $ 6 of the binary mixture is present. It should be noted that the limits of solubility given above for the binary in question Systems made of aluminum-soft metal apply, and that the presence of other, alloying metals, this solubility can noticeably increase or decrease values.

In summary, it can be said that soft metals, such as Lead, bismuth and cadmium can be alloyed with aluminum and cast into a strip, in which at least some of the soft metal is dispersed as generally spherical particles in an aluminum matrix. Of the Strip can then be rolled out and cut into stock blanks in the manner outlined above for improved To maintain storage properties. In general the soft metal (s) forms a smaller proportion, less as about 15 to 20 weight percent of the aluminum based alloy.

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Claims (4)

Claims 1. A method for producing a composite bearing shell, wherein a cast strip is made from a bearing alloy, which contains a larger proportion of aluminum and a smaller proportion of soft metal, and wherein the soft metal as Dispersion of separate, generally spherical particles is present within an aluminum matrix, characterized in that the cast strip is rolled to reduce its thickness in such a way that the generally spherical particles are flattened and elongated in the direction of rolling, the rolled strip in a manner known per se- is rolled onto a backing layer to form a composite strip, a bearing blank of the composite strip in a direction transverse to that general direction of the elongated particles is sheared and a bearing shell is made from the blank in which the elongated particles extend transversely to the direction of rotation of a wave-shaped part which mates with the storage axis. 2. The method according to claim 1, characterized in that lead, cadmium or bismuth is used as the soft metal. 3 «Method according to claim 2, characterized in that lead is used as the soft metal, and this is present in the alloy in an amount of about 1-10 weight percent. 4. Composite bearing shell consisting of an inner layer made of an aluminum bearing alloy, which has a larger proportion Contains aluminum and a smaller proportion of a soft metal and wherein the inner layer is rolled together with an outer backing layer, thereby g e k e η η - 009820/1342 shows that the soft metal as elongated, flat particles, which are distributed within an aluminum matrix, exists and the general direction of the elongated particles perpendicular to the intended direction of rotation of an undulating Part lies, which fits together with the bearing shell. 5 · composite bearing shell according to claim 4, characterized in that the soft metal is lead, which in is present in an amount of about 1-10% by weight. - 12 - ^Bau or, g, _NAl 00 9 8 2 0/1342 Empty soap